internal/lsp/lsprpc: increase timeout for TestEnvForwarding

Some slow builders need more time to get ready.

Updates golang/go#49503

Change-Id: I9225ef43b1fdeb5195467331c7b779fb11dd0e7e
Reviewed-on: https://go-review.googlesource.com/c/tools/+/362976
Trust: Hyang-Ah Hana Kim <hyangah@gmail.com>
Run-TryBot: Hyang-Ah Hana Kim <hyangah@gmail.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>

internal/lsp/lsprpc/lsprpc_test.go

@@ -294,7 +294,7 @@ func (s *initServer) Initialize(ctx context.Context, params *protocol.ParamIniti
 func TestEnvForwarding(t *testing.T) {
 	testenv.NeedsGo1Point(t, 13)
 	server := &initServer{}
-	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
 	defer cancel()
 	_, tsForwarded, cleanup := setupForwarding(ctx, t, server)
 	defer cleanup()